Zinc base casting alloys



Patented Mar. 18, 1952 7 ZINC BASE CASTING ALLOYS Sidney Kornblum, Brooklyn, N. Y.

No Drawing. Application January 2, 1952, Serial No. 264,655

3 Claims. (Cl. 75-17 8) This invention relates to zinc base alloys and more particularly to a zinc base alloy having improved characteristics. The instant application is a continuation in-part of my co'pending application Serial Number 122,581, filed October-20th, 1949.

Zinc base alloys have found considerable application particularly in the production of die or gravity castings. In the gravity casting process themolten metal which may be in'the form of an alloy is poured into molds and flow into, and fills the cavities thereof by the action of gravity. In the die casting process the molten metal which may be in the form of an alloy is introduced into the molds or dies and is injected into, and fills the cavities thereof, under pressure. In order to produce castings of good quality by these methods, a high degree of fluidity in the molten state is desirable, particularly when castings having intricate shapes or fine detail are to be produced. Additionally, fine grain size in .the metal has been found to reduce the amount of occluded air or gases in the finished castings thereby reducing the tendency of the cast product to deteriorate and providing a smoother-surface thereon as well as increasing the tensile strength thereof.

vA particularlv desired characteristic in such alloys is one which will produce castings wherein pores or cavities at the surface are reduced or elim nated. Such pores-or cavities tend to trap portions of the plat n solutions in which the castings may be immersed during t e plating process as a result of which undesirable spitouts or breaks in t e plated surface are formed. The reduction or elimination of pores or cavities at t e surface of the castinesalso permits of the produ tion of a plated castma capable of presenting a hi hly lustrous finished surface.

It is an obiect of t is invention to form zinc ba e allo s havin a hi h de ree of fluidity in the r molten state whereby such allo s are particu arl su table for use in formin cast ob ects part cular v hv gra it an die castin methods.

It is a further ohiect of this invention to roduce such allo s ca able of producing castings having a'fine grain structure.

An additional object of this invention is the production of alloys wherein surface pores or cavities are largely reduced or eliminated as is the de ree of air or gases occluded therein.

" In. order to accomplish these and other purposes zinc base alloys are produced by the addition of zirconium thereto during the alloying process. The zirconium may be introduced in the form of a master or pre-alloy or it may be in the form of a zirconium salt.

The use of zinc base alloys as has heretofore been indicated is conventional in the gravity casting art. As presently practiced, such alloys are generally formed of approximately 95% zinc and 5% aluminum or approximately 94 /2% zinc and 5%% aluminum. Such zinc base alloys have found wide application and the invention will therefore be described as applied to alloys of the above general type. The addition of zirconium is also advantageous in zinc base casting alloys containing from 3.5% to 4.5% aluminum, copper up to 3.5% and magnesium up to .10%.

In forming the alloys comprising the invention, it has been found advantageous to incorporate the zirconium therein in the form of a zirconium salt, preferably potassium zirconium fluoride, K2ZI'F6, during the alloying process. The alloys may be prepared by introducing the zinc and aluminum together with the potassium zirconium fluoride into a, crucible or similar ves- 'sel and then melting the whole. The alloys have also been prepared by forming a bath of a portion of the ultimate zinc content thereof together with a portion of the zirconium salt. The additional metal to be alloyed therewith, such as aluminum, is then added and followed by the addition of the remaining zinc and zirconium salt. The zirconium salt may also be introduced into the bath after the components of the allo are in, molten state. T e alloys in accordance with the present invention ha e been prepared by forming an alovingbath containing appro imately 94 /270 zinc and 5 aluminum and adding from .0'125.% to 1.0% o potass um z rconium fluoride thereto. The rconium. salt ma be added in the manner ind cated. Similar improvements in the characteristics of the allov have been achieved by the use of a proxim tely 95% zinc and 5% aluminum and. t e ad ition of from .0125% to 1.0% of pot ium ircon um fluoride t ereto.

T e allo s may a so be advanta eously prepared b forminc. a bath of approximately 10% of the ultimate z nc content and about 50% of the ultimate amount of zirconium salt, the aluminum ma then be added and followed by the rem'minins zinc and z r on um salt after the aluminum has been inc rporated into the bath. The

alloyin bath may then he fluxed by conventional and. -.alurninum in said pro ortions demonstrate a marked improvement in the fluidity during the casting process. The cast products thus produced have finer grain structure as compared with those of the prior art and manifest a lower porosity and a smoot er surfa e which is characterized by a reduction or elimination of pores or cavities. The tensile strength of the product is similarly improved.

Specific batches of the alloy having the improved characteristics have also been prepared by introducing 2,000 pounds of zinc, 100 pounds of aluminum and 4 ounces of potassium zirconium fluoride into a crucible and forming a common melt therefrom.

In addition the alloy having the improved characteristic has been prepared by using 2,000 pounds of zinc, 90 pounds of aluminum and 20 pounds of potassium zirconium fluoride.

As has heretofore been indicated, zinc base alloys for die casting purposes are also generally utilized in the art. Typicalexamples of alloys suitable for this purpose are enumerated in A. S. T. M. specification 386-43 and designated as alloys XXI, XXIII and XXV. These alloys have as their principal components aluminum, magnesium, copper and zinc. Impurities may be present in the maximum quantities indicated in said specifications. Since such zinc base alloys have found wide application, the invention will also be described as applied to alloys of this general type.

The principal components of the alloys as specified in the above A. S. T. M. specification may vary within the limits of the following percentages:

XXI XXIII XXV Copper 2.5 to 3.5.... 011 Max. .75 to 1.25. Aluminum. 3.5 to 4.5 3.5 to 4.3..-. 3.5 to 4.3. Magnesium .02 to .10.... .03 to .08.... .03 to .08. Zinc." Remaindcrm Rcmainder.. Remainder.

be introduced into the alloy bath in the form of a master or pre-alloy as in the form of a commercially available pre'-alloy with magnesium. It may also be advantageously incorporated in the form of a potassium zirconium fluoride in the manner heretofore indicated. The

zirconium salt is added in the amounts indicated by the above percentages for zirconium.

pounds of zinc, 78 pounds of aluminum, 17.6 ounces of magnesium, 1 pound of copper and 8 ounces of zirconium.

The alloy has also been prepared by using 2,000 pounds of zinc, 78 pounds of aluminum, 13 ounces of magnesium, 20 pounds of copper and 6 ounces of zirconium.

Substitution of a like amount of potassium zirconium fluoride for the zirconium in the above batches results in alloys of similarly improved characteristics.

In all of the batches prepared as herein indicated variation of the amount of zirconium or potassium zirconium fluoride introduced into the alloying bath from 4 ounces to 20 pounds produces similarly improved characteristics in the resulting alloys.

The percentages herein stated are percentages by weight.

I claim:

1. A zinc base casting alloy characterized by a high degree of fluidity in molten state and the substantial elimination of surface porosity in the objects therefrom consisting of from 91.9% to 98.48% zinc, from 3.5% to 4.5% aluminum, up to 3.5% copper and from .02% to .10% magnesium, to which has been added, zirconium in an amount from .0125% to 1.0% of the total weight of the other metals comprising the alloy.

2. A zinc base casting alloy characterized by a high degree of fluidity in molten state and the substantial elimination of surface porosity in the objects cast therefrom consisting of from 91.9%

' to 93.98% zinc, from 3.5% to 4.5% aluminum,

Comparison of the alloys thus produced with control die casting alloys of the prior art demonstrate a marked improvement in the fluidity during the casting process. The cast products thus produced have finer grain structure as compared with those of the prior art and manifest a lower porosity and a smoother surface which is characterized by a reduction or elimination of pores or cavities. The tensile strength of the product is similarly improved.

Specific batches of the alloy having the improved characteristics have also been prepared by using 2,000 pounds of zinc, 80 pounds of aluminum, 12.8 ounces of magnesium, 60 pounds of copper and 8 ounces of zirconium.

The alloy having the improved characteristics has additionally been prepared by using 2,000

from 2.5% to 3.5% copper and from .02% to .10%

magnesium, to which has been added zirconium in an amount from .0125% to 1.0% of the total weight of the other metals comprising the alloy.

3. A zinc base casting alloy characterized by a high degree of fluidity in molten state and the substantial elimination of surface porosity in the objects cast therefrom consisting of from 94.37% to 95.72% zinc, from 3.5% to 4.3% aluminum, from .75% to 1.25% copper and from .03% to 08% magnesium, to which has, been added zirconium in an amount from .0125% to 1.0% of the total weight of the other metals comprising the alloy.

SIDNEY KORNBLUM.

REFERENCES CITED The following references areof record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,364,654 Tedesco Jan. 4, 1921 2,013,870 Starmann Sept. 10, 1935 2,317,179 Daesen Apr. 20, 1943 FOREIGN PATENTS Number Country Date 462,052 Great Britain Feb. 22, 1937 560,281 Germany "Sept. 30, 1932 OTHER REFERENCES Materials and Methods, November 1945, page 1444. 

1. A ZINC BASE CASTING ALLOY CHARACTERIZED BY A HIGH DEGREE OF FLUIDITY IN MOLTEN STATE AND THE SUBSTANTIAL ELIMINATION OF SURFACE POROSITY IN THE OBJECTS THEREFROM CONSISTING OF FROM 91.9% TO 96.48% ZINC, FROM 3.5% TO 4.5% ALUMINUM, UP TO 3.5% COPPER AND FROM .02% TO .10% MAGNESIUM, TO WHICH HAS BEEN ADDED ZIRCONIUM IN AN AMOUNT FROM .0125% TO 1.0% OF THE TOTAL WEIGHT OF THE OTHER METALS COMPRISING THE ALLOY. 